MC68HC908GZ16 Datasheet, PDF (222/314 Pages) Motorola, Inc – Microcontrollers

System Integration Module (SIM)
Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The
arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is
latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched
interrupt is serviced (or the I bit is cleared). See Figure 16-10.
MODULE
INTERRUPT
I BIT
IAB
IDB
R/W
DUMMY
SP
SP – 1 SP – 2 SP – 3 SP – 4 VECT H VECT L START ADDR
DUMMY PC – 1[7:0] PC – 1[15:8] X
A
CCR V DATA H V DATA L OPCODE
Figure 16-8. Interrupt Entry Timing
MODULE
INTERRUPT
I BIT
IAB
IDB
R/W
SP – 4 SP – 3 SP – 2 SP – 1
SP
PC
PC + 1
CCR
A
X PC – 1 [7:0] PC – 1 [15:8] OPCODE OPERAND
Figure 16-9. Interrupt Recovery Timing
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 1
222
Freescale Semiconductor